Sometimes it is difficult or impossible to determine when a bad habit started, but for the Giants it’s quite easy. Look no further than Oct. 16 in Dallas as the time and the game that spawned a trend that has nagged the Giants ever since.

It could be a failing that proves to be the difference in a rousing playoff run or a deflating flop to the finish as they brace for the arrival of the Cowboys for Sunday’s first-place showdown at Giants Stadium.

In the 16-13 overtime loss six weeks ago to the Cowboys at Texas Stadium, the Giants started slowly, tentatively, with Eli Manning looking young and restless, with an offense that has all the tools but can’t get them out of the shed. They became embroiled in a taut, tense game, falling behind and inhaling the scent of desperation before they staged a frantic, furious and fantastic finish. Then they fell short.

The Giants would like to believe they’ve learned and grown from that past experience, but in truth they’ve written and re-written the same script, riding a dangerous wave to victory against the Broncos and crashing down in losses to the Vikings and Seahawks.

“That was the game where our defense really started playing well,” Tiki Barber said. “They kept us in it despite our poor and inconsistent offensive performance.

“Unfortunately, that’s been an M.O. for us this season. We’re only scoring when we have to score. But it should never come to that. We should be able to play with a sense of urgency and consistency that allows these games not to come down to the last two minutes of every one.”

That’s the exact scenario that played out in Dallas earlier this season, as the Giants scored their first and only touchdown with 25 seconds left in the fourth quarter, then lost the coin toss and were beaten in overtime.

“We’re doing a good job of getting into the fourth quarter, staying in there,” Manning said. “We’d like to have the lead, we’re finding ways to make it a game and give ourselves a chance, we just have to figure out a way to take it to the next level.”

After that loss, Barber and Plaxico Burress decried the Giants were out-coached, with Burress saying his offense was “a step behind” and Barber insinuating that the Giants gave up on the running game far too early.

“I don’t think they game-planned better, we just couldn’t catch up with them offensively,” Burress said this week. “We did some things that definitely hurt us.”

Like starting too slow and seeing a comeback fall short, a habit the Giants know they need to break.